Box springs or bedding foundations have traditionally included coil springs positioned in a vertical orientation so as to provide resilient support for a bedding mattress. In an effort to improve upon these conventional coil spring types of box spring or bedding foundation assemblies, numerous prior art assemblies have been developed which substitute modular wire springs for the more traditional coil springs. "Modular wire" springs is a term of art used to describe springs which derive their resiliency from torsion bars or configurations other than coils. Examples of modular wire springs embodied in box spring assemblies are to be found in U.S. Pat. Nos. 3,825,960; 3,833,948; and 3,835,485. Additionally, some prior art box spring assemblies have been developed which include combinations of coil and modular wire springs, as for example, the box spring assembly shown in U.S. Pat. No. 3,990,121. In those instances wherein modular wire springs and coil springs have been combined in a box spring, the modular wire springs have usually functioned to impart additional firmness to selected areas of the box spring, as for example, around the edge of the box spring or in the center section of the box spring.
A limitation of modular wire springs has been the relative smallness of the area of the top rectangular grid supported by the modular wire spring. A larger support area for the rectangular grid would improve the overall support provided by the box spring assembly.
One problem associated with some modular wire springs is the lack of resiliency and softness of the support provided by the spring, particularly upon initial deflection of the springs. Modular wire springs are very resilient, i.e., bounce back from deflection, but do not provide the relatively soft support or deflection characteristics achievable by coil springs. What is needed is a spring which has the softness or feel of coil springs in a resilient modular wire spring.
It has therefore been an objective of this invention to provide an improved box spring with greater support for a larger area of the top rectangular grid.
Still another objective of the present invention has been to provide a modular wire spring that maintains the resiliency of previously known modular wire springs while providing softer resilient support.